The present invention relates generally to a mechanical filter gauge for determining the filtering capability of a vehicle filter, and in particular to a mechanical gauge for measuring and displaying the functionality of a vehicle's air filter.
The improved device of the present invention is used in connection with an air filter for internal combustion engines. It is particularly useful for application to turbocharged diesel engines on trucks, tractors and industrial and marine applications. The device indicates and locks itself in position, and activates a signaling device on the vehicle dashboard, when the air filter has become so loaded with contaminants that the supply of air required by the engine for its operating efficiency is not being drawn through the filter and that the filter therefore requires cleaning or replacement. It also locks itself in various positions to provide a continuous indication as to how much useful life remains in the air filter before is should be cleaned or changed.
The use of a gauge to monitor the filtering ability of a vehicle's air filter is known in the art. However, the prior art combination of such a gauge with a switch to positively actuate a dashboard indicator light of the filter's condition, without flickering or giving an otherwise unclear signal, based on the status of the gauge, is new in the art. In particular, the dashboard light signal could sometimes light before the gauge actually reached "redline," or the point at which the air filter required replacement. Further, the dashboard light signal could flicker or not remain lit after the gauge had reached redline. The mere presence of the gauge and dashboard indicator will in most cases cause the driver of the vehicle to rely on the signal being given. However, if a signal is unclear, or gives a false indication that the filter is not yet in need of replacement, serious engine damage could result.
Earlier patents in this area include U.S. Pat. No. 4,369,728, issued to Nelson on Jan. 25, 1983, and U.S. Pat. No. 4,445,456, issued to Nelson on May 1, 1984. However, the signal in the vehicle and the gauge near the engine would not always agree with each other using these prior art devices. Further, the dashboard light would not always remain on until the filter was serviced and the gauge reset. Also, as disclosed, these switches were relatively expensive to manufacture and assemble.
Additionally, prior art indicators have not always been easy to fully reset, sometimes resulting in a gauge that may give a false, premature signal that an air filter requires replacement. This may in turn result in unnecessary filter maintenance.